Low compression golf ball

ABSTRACT

This invention relates to the use of chemical compounds to trap carbon-centered radicals during the golf ball curing process. The intended end result is a golf ball that has lower compression due to a decrease in crosslink density while retaining sufficient crosslink density to impart durability to the golf ball and either maintain or increase the resiliency of the golf ball. The subject invention more specifically discloses a golf ball which is comprised of a solid core and a resin cover wherein the core is produced by curing a composition comprising an elastomeric polymer, a free radical initiator, a radical crosslinking agent, and at least one carbon-centered radical trap, wherein the carbon-centered radical trap is free of sulfur, and wherein the carbon-centered radical trap is not a stable free radical. The present invention further discloses a process for manufacturing a golf ball core which comprises (1) blending a mixture of an elastomeric polymer, a free radical initiator, a radical crosslinking agent, and at least one carbon-centered radical trap to produce a golf ball core composition, wherein the carbon-centered radical trap is free of sulfur, and wherein the carbon-centered radical trap is not a stable free radical, (2) compressing the golf ball core composition into an essentially spherical shape to produce an uncured golf ball core and (3) heating the uncured golf ball cure at an elevated temperature to produce a cured golf ball core.

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/616,110, filed on Oct. 5, 2004, and incorporatesherein by reference the teaching thereof in their entirety.

FIELD OF THE INVENTION

This invention relates to the use of chemical compounds to trapcarbon-centered radicals during the golf ball curing process. Theintended end result is a golf ball that has lower compression due to adecrease in crosslink density while retaining sufficient crosslinkdensity to impart durability to the golf ball and either maintain orincrease the resiliency of the golf ball.

BACKGROUND OF THE INVENTION

Golfers desire golf balls with high resiliency, which translates intoimproved flight distance. While desiring a long flight distance, golfersare also accustomed to a particular range of feel and sound from thegolf ball. In general, an increase in resiliency can be obtained bymanipulating the golf ball formulation. The problem with this approachhowever, is that augmentations to the formulation that would result inimproved resiliency typically increase the rigidity of the golf ball.This increase in rigidity translates into a decreased feel for theplayer. As a result, there has traditionally been a trade-off in thedesign of golf ball cores between hitting feel and distance. Thelongstanding goal of golf ball manufacturers has been to construct golfballs capable of long flight distance without compromising a soft feel.

In general, golf balls may be divided into two categories: solid andwound. The wound golf ball has been viewed as a premier ball given itssoft feel and high spin rate. Wound golf balls typically include a solidor fluid-filled center surrounded by a tensioned elastomeric thread anda cover. Wound balls generally are more difficult and expensive tomanufacture than solid golf balls. Solid golf balls include one-piececonstructions, two-piece constructions comprised of an elastomeric-basedcore and a cover, and three-piece and multi-layer balls which typicallyhave an elastomeric-based core, at least one intermediate layer, and acover. The elastomer-based cores typically represent the greatest volumewithin the golf ball. One-piece balls are the simplest and leastexpensive to manufacture but do not offer the desired playingcharacteristics. Their performance typically relegates them to use asrange balls. The two-piece construction offers improved playingcharacteristics while being relatively easy to manufacture.

The solid golf balls or cores of wound balls generally have anelastomeric-based core that is formed by compression molding withsubsequent vulcanization. In the case of a one-piece ball, the entireball is constructed by this process. Polybutadiene of 90% or greatercis-content is generally preferred for golf balls possessing the bestbalance between feel and distance. The polybutadiene polymer isgenerally formulated with a free radical coagent and a free radicalsource. The free radical coagent is most often a metal salt of anα,β-ethylenically unsaturated carboxylic acid. The free radical sourceis predominantly a peroxide or combinations of peroxides. The freeradical coagent is believed to both homopolymerize as well as graft tothe polybutadiene during the crosslinking reaction. During this process,a high modulus filler is created in situ with connection to theelastomeric matrix. The result is a compound with sufficient rigidity,resiliency, and durability for golf ball play.

U.S. Pat. No. 4,056,269 and U.S. Pat. No. 4,264,075 disclosed a moldedgolf ball employing a filler-functioning cross-linking monomercomprising a polyvalent metal salt of an unsaturated acid. At sufficientlevels of filler-functioning cross-linking monomer, the golf ballcomposition comprising cis-polybutadiene elastomer was reported to havegood properties. However, it was also reported that the curing processgenerated an exotherm during the vulcanization step. The exotherm wasreported to exceed the temperature of the mold by 60° C. This resultedin an internal temperature of 220° C.

The exotherm reported on curing the golf ball core composition is likelydue to the expected exotherm that would be seen from the free radicalinitiated homopolymerization of the coagent in such a viscous medium aspolybutadiene elastomer. As the internal temperature of the compoundincreases, the rate of decomposition of peroxide to free radicals alsoincreases. Once decomposed, the oxygen-centered radical from theperoxide has the ability to both abstract a hydrogen radical from thepolybutadiene or add to the double bond which is typically present incommon peroxide coagents. As the flux of radicals in the systemincreases, the homopolymerization and grafting reactions also increase.This situation whereby the temperature increases the rate of anexothermic reaction which in turn continues to raise the temperature isclassically termed a “runaway”. It is speculated here that during thisrunaway time frame, the extent of cure experiences an asymptoticincrease. The difficulty lies in the fact that to reach a necessarydegree of crosslinking there needs to be a sufficient amount ofpolymerizable coagent as reported in U.S. Pat. No. 4,056,269 and U.S.Pat. No. 4,264,075. However, it was also reported that the exothermgenerated during the curing step made the molding process moredifficult. If a golf ball core is formulated with a lower level ofpolymerizable coagent, the resiliency and durability of the ball arecompromised. However, the degree of exotherm found during the cure isless and the time for complete conversion of the peroxide is converselymuch longer. By formulating a golf ball core with a sufficient amount ofpolymerizable coagent for reasonable golf ball performance, an exothermis created which is sufficient to induce further decomposition ofperoxide. The increase in decomposition of peroxide introduces moreradicals and an increase in the homopolymerization and graftingreactions. The ability to control the exotherm by cooling is limited bythe dimensions of the ball, which offer very little surface area tovolume. The result is a rapid increase in crosslink density that may beabove that necessary for reasonable golf ball play.

There have been several citations in the patent literature whichdisclose the addition of a chemical agent to augment the properties of agolf ball. The augmentation has typically involved a decrease incompression.

U.S. Pat. No. 4,852,884 discloses a golf ball which exhibits a highcoefficient of restitution when a metallic dithiocarbamate is used atlevels between 0.1 and 0.5 parts by weight based on 100 parts of apolybutadiene elastomer or mixtures thereof. No disclosure is made as tothe mechanism of improvement from the dithiocarbamate.

U.S. Pat. No. 4,650,193 discloses the creation of a soft layerunderneath the golf ball cover. This is accomplished by modifying thecure at the surface of a golf ball during the molding process. Themodification occurs by exposing the surface to an agent that alters thecure. The only example and claim to a suitable agent is elementalpowdered sulfur.

U.S. Pat. No. 5,252,652 first discloses the use of an organic sulfurcompound and/or a metal salt thereof. The addition of said organicsulfur compound and/or a metal salt thereof to the rubber golf ball corecomposition produced a rubbery elastomer having improved reboundresilience after vulcanized. As a golf ball, the result produced by thecompound is cited as an increase in initial velocity upon hitting andimproved flying performance. No disclosure is made as to the mechanismof improvement from the organic sulfur compound and/or metal saltthereof.

U.S. Pat. No. 6,184,301 discloses the use of a sulfur halide to impart asolid golf ball with a good degree of both deformation and resiliency.In the final golf ball, the results translate into improved flightdistance while maintaining a good feel. No disclosure is made as to themechanism of improvement from the sulfur halide.

U.S. Pat. No. 6,666,780 and U.S. Pat. No. 6,679,791 disclose the designof a multi-piece golf ball whereby there exists an optimized hardnessprofile in which the hardness gradually increases radially outward fromthe center toward the outside edge or surface of the core. Thisconstruction feature is said to provide improved rebound energy, traveldistance, durability, and feel of the ball. The patents offer suitablecompounding ingredients such as a thiophenol, thionaphthol, halogenatedthiophenol or metal salt thereof in order to obtain said hardnessgradient. No disclosure is made in either patent as to the mechanism ofimprovement from the suggested suitable compounding ingredients.

U.S. Pat. No. 6,162,135 and U.S. Pat. No. 6,291,592 disclose the use ofa cis-to-trans catalyst to produce golf balls with lower compression andincreased resilience. The cis-to-trans catalyst will isomerize a portionof the cis-polybutadiene to the trans-configuration yielding a greatertrans-polybutadiene content after curing than was originally present.The cis-to-trans catalyst can be applied to the center, intermediatelayer, or both, depending on the golf ball construction. The lowermodulus and increased resilience is explained, without being bound tothis particular theory, by the increased mobility of the polymerbackbones as a result of the combination of cis- andtrans-polybutadiene.

U.S. Pat. No. 6,635,716 discloses the use of a halogenated organosulfurcompound or metal salt thereof to increase the coefficient ofrestitution (“COR”) and/or decrease compression. The halogenatedorganosulfur compound is introduced at levels between 2.2 and 5.0 partsper hundred polybutadiene. No description is given as to the mechanismby which the halogenated organosulfur compound improves COR or decreasescompression.

U.S. Pat. No. 5,697,856 and U.S. Pat. No. 6,287,218 discloses the use ofan organosulfur compound in combination with polybutadiene rubber of 90%or greater cis content to affect an increase in the trans-polybutadienecontent upon curing to between 10% and 30% for the first patent and 10%to 50% for the second. The presence of the organosulfur compound isreported to generate a gradient in crosslinking from the center of thecore to the exterior. The resultant golf ball has a lower compressionwhile maintaining or increasing resiliency.

U.S. Pat. No. 5,711,723 and U.S. Pat. No. 5,776,012 disclose theconstruction of a three-piece golf ball wherein the core and shellregions have different hardness. The difference in hardness between coreand shell is brought about by the placement of a crosslinking adjusterin the core composition. The construction is reported to provideimproved flight distance and feel. The benefit of the organosulfurcompound and metal-containing organosulfur compound is said to be aresult of the accelerated mastication of the rubber, and the resultingenhancement of the rebound performance of the soft part of the core.

U.S. Pat. No. 5,919,101 discloses a three-piece golf ball wherein thecore of the golf ball employs an organic sulfide compound. The inventionis described to provide a golf ball with good shot feel whilemaintaining excellent flight performance and durability.

In all of the cited prior art, with each invention there is the additionof a chemical agent that yields improved golf ball performance. In manyof the citations here, the chemical radicals in unsaturated polymers mayeither cause an increase in crosslink density or cause the polymer toundergo chain scission. The tendency for either of the reactions and thedegree to which they occur is dependent upon the chemical nature of thepolymer in question. Radical traps are those reagents that react withradicals in a way that generally creates a covalent bond and eliminatesthe radical character. An example of a common commercial radical trap isan antioxidant. It is well known in the stabilization of unsaturatedpolymers that peroxides may form along the backbone of the polymerchain. Upon the decomposition of the peroxide, an oxygen-centeredradical is generated. The antioxidant, typically having the chemicalmoieties of amine, sulfur, etc. eliminates the radical nature of theperoxide fragment by either addition of a segment from its compositionor by whole addition to the oxygen-centered radical. The action of theantioxidant to trap the newly formed radical may occur prior to theradical being transferred to the polymer or subsequent to the transfer.

The prior art is void of detail with regard to the mechanism by whichthe chemical agents described therein impart improved golf ballperformance. However, a theory regarding such a mechanism is advancedtherein and is used to expand the nature and scope of chemical agentsthat can be employed. By utilizing the principles delineated hereinbetter golf balls can be manufactured using chemical agents that aretypically less costly and more readily accepted in commercialapplications.

SUMMARY OF THE INVENTION

This invention is based upon the determination that the mechanism bywhich the cure of golf ball cores is optimally altered is one wherebythe chemical agent used permits the peroxide to decompose and transferthe radical to the polymer by either addition or abstraction. Thechemical agents do not interfere with this crosslinking initiation step.Once the radical is transferred and exists as a carbon-centered radical,the chemical agent disrupts the cure by either mitigating thehomopolymerization reaction of the crosslinking coagent or thecross-over polymerization within the unsaturated core polymer, or both.The prior art that has been previously reviewed herein identifies anumber of chemical agents that are believed to perform in this way.

General classifications of the type of chemical agents that may be usedto disrupt the radical cure include free radical polymerizationinhibitors or retarders, stable free radicals, peptizing agents, andspin traps. More specifically, the chemical agents in these categoriesshould not have a moiety that can be abstracted by an oxygen-centeredradical, thereby terminating the crosslinking reaction prematurely.Generically in order to offer a composition which is lower incompression while maintaining or improving coefficient of restitution.

The reference Tudos, F.; Foldes-Berezsnich, T. Free RadicalPolymerization identifies polymerization inhibitors and retardersaccording to families of chemistry. These are chemical species thatreact with free radicals to either quench the radical character of thespecies or reduce its rate of propagation. Those families that wereidentified include: vinyl monomers, aromatic hydrocarbons, quinones,aromatic nitro compounds, nitroso compounds and nitrones, and aromaticamines.

The invention relates to the use of a carbon-centered radical trap in agolf ball formulation which includes an amount of polybutadiene, a freeradical source, and a crosslinking coagent, such that the reactionproduct of the formulation has a lower extent of cure than would bepresent without said agent to trap carbon-centered radicals. Thisreduction in cure translates into reduced compression and a softer feelfrom the finished ball. Concurrently, the resiliency and flight distanceof the compound may be increased or decreased by the presence of thecarbon-centered radical trap.

Accordingly, the present invention describes solid golf balls whichinclude a core and a resin cover. The solid golf ball design can includea core obtained by one piece molding or be of a multi-piece design whereone or more layers are coated onto the core. In any case, such solidgolf balls of this invention include a resilient portion obtained byvulcanizing an elastomeric rubber containing composition, which alsoincludes a co-crosslinking agent, a free radical initiator, and acarbon-centered radical trap.

This invention more specifically discloses a golf ball which iscomprised of a solid core and a resin cover wherein the core is producedby curing a composition comprising an elastomeric polymer, a freeradical initiator, a radical crosslinking agent, and at least onecarbon-centered radical trap, wherein the carbon-centered radical trapis free of sulfur, and wherein the carbon-centered radical trap is not astable free radical.

The present invention also reveals a process for manufacturing a golfball core which comprises (1) blending a mixture of an elastomericpolymer, a free radical initiator, a radical crosslinking agent, and atleast one carbon-centered radical trap to produce a golf ball corecomposition, wherein the carbon-centered radical trap is free of sulfur,and wherein the carbon-centered radical trap is not a stable freeradical, (2) compressing the golf ball core composition into anessentially spherical shape to produce an uncured golf ball core and (3)heating the uncured golf ball cure at an elevated temperature to producea cured golf ball core.

DETAILED DESCRIPTION OF THE INVENTION

The elastomeric core and potential intermediate layers may beconstructed with natural rubber and/or synthetic elastomers.Polybutadiene containing at least 80% cis content is preferred. Inaddition to the cis-1,4-polybutadiene rubber, the resilient portion ofthe golf ball may also contain additional rubbers, such asstyrene-butadiene rubber, natural rubber, synthetic polyisoprene rubber,styrene-isoprene rubber, and the like. The amount of such additionalrubbers that can be included in the resilient portion of the golf ballwill normally be no more than about 60 phr (parts per 100 parts byweight of rubber), based upon the total amount of rubber included in theresilient portion of the golf ball. Thus, the resilient portion of thegolf ball will normally contain from about 40 phr to 100 phr of thecis-1,4-polybutadiene and from 0 phr to about 60 phr of such additionalrubbers. It is normally preferred for such additional rubbers to bepresent in the resilient portion of the golf ball at a level of no morethan about 30 phr. It is normally more preferred for such additionalrubbers to be present in the resilient portion of the golf ball at alevel of no more than about 15 phr.

The co-crosslinking agent used in the resilient portion of the golf ballwill typically be an unsaturated carboxylic acid or a metal saltthereof. For example, the co-crosslinking agent can be acrylic acid,methacrylic acid, zinc acrylate, zinc methacrylate or a mixture thereof.The co-crosslinking agent will typically be present in the rubberycomponent of the golf ball at a level which is within the range of about15 phr to about 60 phr. The co-crosslinking agent will typically bepresent in the resilient portion of the golf ball at a level which iswithin the range of about 25 phr to about 40 phr.

The peroxide used in the resilient portion of the golf ball willtypically be an organic peroxide, such as dicumyl peroxide,t-butylperoxybenzoate or di-t-butylperoxide. It is normally preferred touse dicumyl peroxide in such golf ball compounds. The peroxide willtypically be present in the rubbery component of the golf ball at alevel which is within the range of about 0.5 phr to about 3 phr. Theperoxide will preferably be present in the rubbery component of the golfball at a level that is within the range of about 1 phr to about 2.5phr.

Solid golf balls generally include a core and a resin cover. The solidgolf ball design may include a core obtained by one piece molding or beof a multi-piece design where one or more layers are coated onto thecore. In any case, such solid golf balls of this invention include aresilient portion obtained by vulcanizing a cis-1,4-polybutadiene rubbercontaining composition which also includes a co-crosslinking agent, aperoxide, and a carbon-centered radical disrupter.

Golf balls normally have a diameter that is within the range of about41.15 mm to about 42.67 mm. To meet standardized weight requirements,the resilient portion of the golf ball will also typically contain afiller. Some representative examples of fillers that can be used includebarium sulfate, zinc oxide, calcium carbonate, silica, and the like.Antidegradants can also be included in the rubbery component of the golfball to protect it from degradation.

The rubber compound for the resilient portion of the golf ball can beprepared by mixing the cis-1,4-polybutadiene, the co-crosslinking agent,the peroxide, the optional filler and any other optional materials byconventional mixing techniques, such as by means of a roller or akneader. The mixing will normally be carried out for about 10 to about30 minutes, preferably about 15 to about 25 minutes, at a temperature of50° C. to 140° C., preferably 70° C. to 120° C.

The solid golf ball can be a one-piece solid golf ball, a two-piecesolid golf ball or a multi-piece solid golf ball. The one-piece solidgolf ball can be prepared by vulcanizing the rubber compound through onepiece molding. The two-piece and multi-piece solid golf balls normallyinclude a solid core which is comprised of the resilient rubberycompound and a resin cover. In the case of multi-piece solid golf balls,the solid core is composed of a center core which is comprised of theresilient rubbery compound and one or more outer layers coated thereon.At least a portion of the solid core is prepared by vulcanizing therubber composition of the present invention. The vulcanization will beconducted at a temperature which is within the range of about 140° C. to170° C. for about 20 minutes to about 40 minutes. The resin cover is onetypically comprised of an ionomer resin or a mixture of ionomer resins.Suitable ionomer resins are commercially available from the MitsuiPolychemical Company under the trade names Himilan® 1707, Himilan® 1706and Himilan® 1605.

For the purposes of explaining the features of this invention, acritical differentiation is made between a carbon-centered radical andan oxygen-centered radical. Most radical traps used in unsaturatedrubber-employing industries are of the type to capture either type ofradical. These radical traps are typically used to increase thestability of the unsaturated rubber to radical processes that occur fromthe formation and decomposition of peroxides. Antioxidants aredetrimental to a peroxide cure for the same reason they impart greaterservice stability to a compound—elimination of radical species. Anantioxidant present in a peroxide cure system will decrease the activityof the peroxide by reacting with the decomposed radical fragments.Higher levels of peroxide are therefore needed to affect a reasonablecure. Although this satisfies the condition for cure, it may leave thecompound deficient in antioxidant for later stability.

Radical traps that only capture carbon-centered radicals are differentfrom the prospective of peroxide cure. Here, a peroxide included in theformulation has the opportunity to decompose to the peroxy radical andeither abstract a hydrogen radical from the polymer or add to theunsaturation. In either case, the radical is now transferred to thepolymer and crosslinking has been initiated. Further reaction thenproceeds by a carbon-centered radical mechanism. It is not until thistime that the carbon-centered radical trap may interfere with thecrosslink propagation reaction.

This invention relates to the use of chemical compounds to trapcarbon-centered radicals during the golf ball curing process. Theintended end result is a golf ball that has lower compression due to adecrease in crosslink density while retaining sufficient crosslinkdensity to impart durability to the golf ball and either maintain orincrease the resiliency of the golf ball. The subject invention morespecifically discloses a golf ball which is comprised of a solid coreand a resin cover wherein the core is produced by curing a compositioncomprising an elastomeric polymer, a free radical initiator, a radicalcrosslinking agent, and at least one carbon-centered radical trap,wherein the carbon-centered radical trap is free of sulfur, and whereinthe carbon-centered radical trap is not a stable free radical. Thepresent invention further discloses a process for manufacturing a golfball core which comprises (1) blending a mixture of an elastomericpolymer, a free radical initiator, a radical crosslinking agent, and atleast one carbon-centered radical trap to produce a golf ball corecomposition, wherein the carbon-centered radical trap is free of sulfur,and wherein the carbon-centered radical trap is not a stable freeradical, (2) compressing the golf ball core composition into anessentially spherical shape to produce an uncured golf ball core and (3)heating the uncured golf ball cure at an elevated temperature to producea cured golf ball core.

The elastomeric core and potential intermediate layers may beconstructed with natural rubber and/or synthetic elastomers.Polybutadiene containing at least 80% cis content is preferred. Inaddition to the cis-1,4-polybutadiene rubber, the resilient portion ofthe golf ball may also contain additional rubbers, such asstyrene-butadiene rubber, natural rubber, synthetic polyisoprene rubber,styrene-isoprene rubber, and the like. The amount of such additionalrubbers that can be included in the resilient portion of the golf ballwill normally be no more than about 60 phr (parts per 100 parts byweight of rubber), based upon the total amount of rubber included in theresilient portion of the golf ball. Thus, the resilient portion of thegolf ball will normally contain from about 40 phr to 100 phr of thecis-1,4-polybutadiene and from 0 phr to about 60 phr of such additionalrubbers. It is normally preferred for such additional rubbers to bepresent in the resilient portion of the golf ball at a level of no morethan about 30 phr. It is normally more preferred for such additionalrubbers to be present in the resilient portion of the golf ball at alevel of no more than about 15 phr.

The co-crosslinking agent used in the resilient portion of the golf ballwill typically be an unsaturated carboxylic acid or a metal saltthereof. For example, the co-crosslinking agent can be acrylic acid,methacrylic acid, zinc acrylate, zinc methacrylate or a mixture thereof.The co-crosslinking agent will typically be present in the rubberycomponent of the golf ball at a level which is within the range of about15 phr to about 60 phr. The co-crosslinking agent will typically bepresent in the resilient portion of the golf ball at a level which iswithin the range of about 25 phr to about 40 phr.

The peroxide used in the resilient portion of the golf ball willtypically be an organic peroxide, such as dicumyl peroxide,t-butylperoxybenzoate or di-t-butylperoxide. It is normally preferred touse dicumyl peroxide in such golf ball compounds. The peroxide willtypically be present in the rubbery component of the golf ball at alevel which is within the range of about 0.5 phr to about 3 phr. Theperoxide will preferably be present in the rubbery component of the golfball at a level that is within the range of about 1 phr to about 2.5phr.

Solid golf balls generally include a core and a resin cover. The solidgolf ball design may include a core obtained by one piece molding or beof a multi-piece design where one or more layers are coated onto thecore. In any case, such solid golf balls of this invention include aresilient portion obtained by vulcanizing a cis-1,4-polybutadiene rubbercontaining composition which also includes a co-crosslinking agent, aperoxide, and a carbon-centered radical disruptor.

Carbon-Centered Radical Disruptors:

Golf balls normally have a diameter that is within the range of about41.15 mm to about 42.67 mm. To meet standardized weight requirements,the resilient portion of the golf ball will also typically contain afiller. Some representative examples of fillers that can be used includebarium sulfate, zinc oxide, calcium carbonate, silica, and the like.Antidegradants can also be included in the rubbery component of the golfball to protect it from degradation.

The rubber compound for the resilient portion of the golf ball can beprepared by mixing the cis-1,4-polybutadiene, the co-crosslinking agent,the peroxide, the optional filler and any other optional materials byconventional mixing techniques, such as by means of a roller or akneader. The mixing will normally be carried out for about 10 to about30 minutes, preferably about 15 to about 25 minutes, at a temperaturewhich is within the range of 50° C. to 140° C., and which is preferablywithin the range of 70° C. to 120° C.

The solid golf ball can be a one-piece solid golf ball, a two-piecesolid golf ball or a multi-piece solid golf ball. The one-piece solidgolf ball can be prepared by vulcanizing the rubber compound through onepiece molding. The two-piece and multi-piece solid golf balls normallyinclude a solid core which is comprised of the resilient rubberycompound and a resin cover. In the case of multi-piece solid golf balls,the solid core is composed of a center core which is comprised of theresilient rubbery compound and one or more outer layers coated thereon.At least a portion of the solid core is prepared by vulcanizing therubber composition of the present invention. The vulcanization will beconducted at a temperature which is within the range of about 140° C. to170° C. for about 20 to 40 minutes. The resin cover is one typicallycomprised of an ionomer resin or a mixture of ionomer resins. Suitableionomer resins are commercially available from the Mitsui PolychemicalCompany under the trade names Himilan® 1707, Himilan® 1706 and Himilan®1605.

While certain representative embodiments and details have been shown forthe purpose of illustrating the subject invention, it will be apparentto those skilled in this art that various changes and modifications canbe made therein without departing from the scope of the subjectinvention.

1. A golf ball which is comprised of a solid core and a resin coverwherein the core is produced by curing a composition comprising anelastomeric polymer, a free radical initiator, a radical crosslinkingagent, and at least one carbon-centered radical trap, wherein thecarbon-centered radical trap is free of sulfur, and wherein thecarbon-centered radical trap is not a stable free radical.
 2. A golfball as specified in claim 1, wherein the carbon-centered radical trapis a chemical agent that disrupts the cross-linking.
 3. A golf ball asspecified in claim 1, wherein the carbon-centered radical trap ispresent in an amount as to decrease the compression by 15%.
 4. A golfball as specified in claim 1, wherein the carbon-centered radical trapis present in an amount as to decrease the compression by 25%.
 5. A golfball as specified in claim 1, wherein the carbon-centered radical trapis present in an amount as to decrease the compression by 50%.
 6. A golfball as specified in claim 1, wherein the carbon-centered radical trapis a free radical polymerization inhibitor.
 7. A golf ball as specifiedin claim 1, wherein the carbon-centered radical trap is a free radicalpolymerization retarder.
 8. A golf ball as specified in claim 1, whereinthe carbon-centered radical trap is a peptizing agent.
 9. A golf ball asspecified in claim 3 wherein the solid core is further comprised of aco-crosslinking agent and a peroxide.
 10. A golf ball as specified inclaim 9 wherein the co-crosslinking agent is present at a level which iswithin the range of about 15 phr to about 60 phr.
 11. A golf ball asspecified in claim 10 wherein the peroxide is present at a level whichis within the range of about 0.5 phr to about 3 phr.
 12. A golf ball asspecified in claim 10 wherein the peroxide is present at a level whichis within the range of about 1 phr to about 2.5 phr.
 13. A golf ball asspecified in claim 9 wherein the co-crosslinking agent is present at alevel which is within the range of about 25 phr to about 40 phr.
 14. Agolf ball as specified in claim 13 wherein said core is furthercomprised of a filler.
 15. A golf ball as specified in claim 14 whereinsaid filler is selected from the group consisting of barium sulfate,zinc oxide, calcium carbonate and silica.
 16. A process formanufacturing a golf ball core which comprises (1) blending a mixture ofan elastomeric polymer, a free radical initiator, a radical crosslinkingagent, and at least one carbon-centered radical trap to produce a golfball core composition, wherein the carbon-centered radical trap is freeof sulfur, and wherein the carbon-centered radical trap is not a stablefree radical, (2) compressing the golf ball core composition into anessentially spherical shape to produce an uncured golf ball core and (3)heating the uncured golf ball cure at an elevated temperature to producea cured golf ball core.
 17. A process as specified in claim 16 whichfurther comprises encapsulating the cured golf ball core with a resincover.
 18. A process as specified in claim 16 wherein the uncured golfball core is heated to a temperature of no more than 470° C. to producethe cured golf ball core.
 19. The golf ball made by the processspecified in claim 16.